The invention relates to optical couplers and particularly to such devices that couple optoelectronic elements and optical fiber. More particularly, the invention relates to couplers having lenses.
Several patent documents may be related to optical coupling between optoelectronic elements and optical media. They include U.S. Pat. No. 6,086,263 by Selli et al., issued Jul. 11, 2000, entitled “Active Device Receptacle” and owned by the assignee of the present application; U.S. Pat. No. 6,302,596 B1 by Cohen et al., issued Oct. 16, 2001, and entitled “Small Form Factor Optoelectronic Receivers”; U.S. Pat. No. 5,692,083 by Bennet, issued Nov. 25, 1997, and entitled “In-Line Unitary Optical Device Mount and Package therefore”; and U.S. Pat. No. 6,536,959 B2, by Kuhn et al., issued Mar. 25, 2003, and entitled “Coupling Configuration for Connecting an Optical Fiber to an Optoelectronic Component”; which are herein incorporated by reference.
In the context of the invention, the optoelectronic element may be understood as being a transmitter or a receiver. When electrically driven, the optoelectronic element in the form of a transmitter or light source converts the electrical signals into optical signals that are transmitted as light signals. On receiving optical signals, the optoelectronic element in the form of a receiver or detector converts these signals into corresponding electrical signals that can be tapped off at the output. In addition, an optical fiber may be understood to be any apparatus for forwarding an optical signal with spatial limitation, in particular preformed optical fibers and so-called waveguides.
A problem with couplers may involve light reflected back to the light source. This may be an issue because, for instance, some fiber optic transmitters suffer from undesirable and performance degrading reflections from the face end of the optical fiber back into the coupled optoelectronic element device (e.g., a semiconductor laser). Here, the fiber's surface and facing surface of the optoelectronic element device form a Fabry-Perot cavity which may modulate the light from the laser transmitter or semiconductor laser and consequently produce unwanted fluctuations in the power coupled to the optical fiber. Further, the optical energy reflected directly into the laser cavity may cause additional noise in the laser's output. For these reasons, it would be desirable to reduce and minimize the return reflections from the fiber face in the coupler.